The present invention is directed to a pedestal rocker seat for coupling a roller bearing adapter and associated rotatable axle to the pedestal of a side frame of a railway car truck, and in particular to a pedestal rocker seat arrangement or assembly that allows transverse rocking movement of the side frame with respect to the axle and that provides passive axle steering.
Rigid railway trucks, such as the SWING MOTION truck manufactured by National Castings Inc., a wholly-owned subsidiary of NACO, Inc., as disclosed in U.S. Pat. Nos. 3,461,814, 3,670,660 and 5,463,964, include two spaced apart parallel side frames and an interconnecting bolster. The truck is made rigid by means of a transom or tubular structure connecting the two side frames together at the height of the side frame spring seats. Such H-frame rigid truck types are used under passenger and freight cars in high speed service and offer improved axle alignment, improved tracking, and increased interaxle shear stiffness over what is provided by non-rigid trucks. However, when a rigid truck negotiates a curve practically all of the guiding force between the rail and the flanges of the wheels on the truck is produced between the leading outer wheel of the leading axle of the truck, while the trailing axle is disposed nearly parallel to a radius of the curve such that the trailing outer wheel of the trailing axle has no predominant flange contact with the rail and thereby no flange force of any appreciable magnitude is generated between the rail and the flange of the outer trailing wheel. Conversely, non-rigid trucks permit part of the guiding force during curving to be taken by the outer trailing wheel of the trailing axle, therefore reducing somewhat the force applied to the flange ofthe leading outer wheel.
Flange force, the force applied between the flange of a wheel and the rail, is one of the important factors in evaluating wheel and rail wear, fuel efficiency, safety and performance of a truck. Many railroad technicians do not look beyond the leading outer wheel of a truck when evaluating a truck's performance. Rigid trucks have therefore often acquired undeserved poor evaluations in spite of good service records. The present invention incorporates passive axle steering in rigid trucks, such as the SWING MOTION trucks manufactured by National Castings, which results in a reduction of the angle of attack between the wheel and the rail during curving, the second most important factor for evaluation of curving performance of a truck, thereby decreasing the flange force on the leading outer wheel, while allowing transverse rocking of the side frame with respect to the axle to control hunting, thereby improving the truck's performance.